The neonatal Fc receptor (FcRn) prolongs the lifespan of both IgG and human serum albumin (HSA), by a pH dependent mechanism, specifically binding both molecules at the acidic pH of the endosome and recycling them back to the cell surface, thus diverting both molecules away from the default lysosomal degradation pathway. It has been shown that FcRn binding capacity is intrinsic to domain-III of albumin.